1. Field of the Invention
The present invention relates to novel compounds for linkers. More particularly, the compounds of the present invention are directed to linkers for peptide synthesis which are useful in the study of peptide chemistry and production of peptide pharmaceuticals.
2. Discussion of the Related Art
Peptide synthesis is very important in peptide research. This is because many peptide amides are bioactive substances, e.g., neurotransmitter hormones, gastrointestinal hormones, and because it is generally difficult to produce them by genetic engineering. Solid-phase peptide synthesis (hereinafter simply abbreviated as "SPPS") was first achieved by Merefield using Boc-amino acid.
In recent years, there have been proposed various methods for efficiently synthesizing peptides at a high purity using an automated peptide synthesizer based on SPPS. Among them, the method using .alpha.-fluorenylmethyloxycarbonyl(Fmoc)-amino acid has recently formed the mainstream of SPPS, because it allows peptide synthesis under mild conditions. In peptide synthesis using the peptide synthesizer, specific cleavage should be carried out between the resin, i.e., solid phase, and the chain to be elongated such as a peptide chain, using an appropriate linker resin, i.e., support. Various linker resins for synthesizing peptide amides have been reported. Examples of the linker resins presently used include those represented by the following formulas: ##STR2## Also, the following tricyclic linkers have recently been reported. ##STR3## However, the linkers mentioned above do not show good reactivity under even milder conditions.